Routes to Heterotrinuclear Metal Siloxide Complexes for Cooperative Activation of O.

The assembly of heterometallic complexes capable of activating dioxygen is synthetically challenging. Here, we report two different approaches for the preparation of heterometallic superoxide complexes [LCr-η-O][MX] (L = OPhSiOSiPhO, MX = [CoCl], [ZnBr], [ZnCl]) starting from the Cr precursor complex [LCr]Li(THF). The first strategy proceeds via the exchange of Li by [MX] through the addition of MX to [LCr]Li(THF) before the reaction with dioxygen, whereas in the second approach a salt metathesis reaction is undertaken after O activation by adding MX to [LCr-η-O]Li(THF).

Investigation of Cubic Fe M Frameworks for Application in Nonaqueous Energy Storage.

Multimetallic complexes have recently seen increased attention as next-generation charge carriers for nonaqueous redox flow batteries. Herein, we report the electrochemical performance of a molecular iron-molybdenum oxido complex, {[(Me TACN)Fe][μ-(MoO κ O,O',O")]} (Fe Mo O ). In symmetric battery charging schematics, Fe Mo O facilitates reversible two-electron storage with coulombic efficiencies >99 % over 100 cycles (5 days) with no molecular decomposition and minimal capacity fade.

Switching from a Chromium(IV) Peroxide to a Chromium(III) Superoxide upon Coordination of a Donor in the trans Position.

O activation at a chromium(II) siloxide complex in propionitrile leads to a chromium(III) complex with an end-on bound superoxide ligand, while the reaction in tetrahydrofuran leads to a side-on peroxo chromium(IV) compound. The superoxide reacts faster with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl hydroxylamine while the peroxide, unlike the superoxide, proved capable of deformylating aldehydes. The system was found to represent a unique case, where even a switching between the two structures can be achieved via the solvent; its ability to coordinate at the position  to the O ligand is decisive, as supported by density functional theory studies.

The Influence of Alkali Metal Ions on the Stability and Reactivity of Chromium(III) Superoxide Moieties Spanned by Siloxide Ligands.

In recent years, it has become clear that the presence of redox-inactive Lewis acidic metal ions can decisively influence the reactivity of metal-dioxygen moieties that are formed in the course of O activation, in molecular complexes, and metalloenzymes. Superoxide species are often formed as the primary intermediates but they are mostly too unstable for a thorough investigation. We report here a series of chromium(III) superoxide complexes [L Cr]M O (THF) (L= OSiPh OSiPh O , M =Li , Na , K and y=4, 5), which could be accessed, studied spectroscopically and partly crystallized at low temperatures.